Preparing caustic potash.



i TE' t rts rename are. y

nsmsrcn arms, or GnrnsHErM-oN-rEn-Mam, GERMANY, nssrcnoa 'ro CHEMISCHE 'FABRIK GRIESHEIM-ELEKTRON, E FRANKFORT-ON-THE-MAIN, GERMANY, A COR- roaa'rion or GERMANY.

caries.

1\To' Drawing.

To all whom it may concern:

Be it known that I, HEINRICH REIT-Z, a

' subject of theGerinan Emperor, and r'esi dent. at Griesheim-on-the-Main, Germany, have invented certain new' and useful Improvements in Preparing Caustic Potash, of which the following is a specification. The present invention relates to an im proved method or process of manufacturing crystallized anhydrous caustic pot-ash.

The German specification No. 189,835 dc.-

' scribes a processfor the production of anhydrousKOH, which process consists in cooling w'hile starring, caustic potash melts and I separating from the mother lye the caustic potash which has crystallized out .of it. If

itbe desired to obtain a rich yield of anhydrous crystals, the caustic potash melts must be concentrated to more than 90,per,cent.-

of KOH. On cooling while stirring, such highly concentrated melts are (ata little over 200 centigrade) so stiff that separation from the mother lye, of the preciph tated crystals is not possible. The precipi= tation ofthe c stals is at that temperature already very a undant; the mother lye is absorbed or sucked up by the crystals and I the resulting pulp is of a drygranular consistency. At'temperatures higher than 200 centigrade the mother lye and crystals could be separated by the process described inthe specification of the German Patent 189,835

but, on account of the high temperature, the

separation is most difiicult and indeed from tain a high yield of crystals of anhydrous KOH, the lye is evaporated at a temperature of about-350 to 370 centigrade, if the evaporation is efiected at ordinary pressure, and at a temperature of 310 to 330 centigrade, it the evaporation takes place in a vacuum, so as to concentrate it to 92 percent, then the melt is allowed 'to cool, while PREPARING CAUSTIC POTASH.

Specification of'LettersPatent. Patgntd Sept, 27, i916), Application'filed December 22, 1909. Serial No. 534,532.

tained, this occurring at from 220, to 250, centigrade, according to the degree of-concentration. As it is then no longer possible toreadily efiect a'separation of the precipitated anhydrous crystals from the mother lye, a melt of KOH of less concentration is 5 added to the said thick pulp. The additional melt must be so constituted that, on cooling below 200 centigrade, it

does not precipitate any considerable amount of crystals. Then; the mixture can be fur ther cooled and the temperature so lowered that separation ofthe cr stals from the lye does not present any di culties.

By correctly choosing the melt used for dilution,- a re dissolution (if the anhydrous KOH crystals takes place, but to a very small extent and the additional melt holds in solution practically allthe impurities.

In cooling the diluted pulp, the tempera ture should not decrease to much below 140 centigrade because, .below' this temperature,

the separation of the KOH crystals containin water begins (Pickeflng Chem. Soc. 1893 o. 63 page 890).

The following example will illustrate how this invention may be performed but the invention is not limited to the details of this example: 3 kilograms of 93.7 per cent. potash produced fiom. a 50 per cent. commercial lye are cooled to 220 centigrade while being stirred, and, after. fiirther' cooling, about 600 grams of a meltcf 85.6 per cent. of potash are addedlittle by little until the temperabeing stirred, until the thick pulp is chture has lessened to about 140 centigrade,

and then, at this temperature, the mass is treated-, in a hydro extractor. About 7 0 per centfof crystalscontaining 99.5 per cent. potash are obtained.- Y

If melts containing to 92 per cent.

potash be treated, the yield of anhydrous KGHcrystals only amounts to from 30 to 45 percent. of the weight of the concentrated melt. I claim In the manufacture of anhydrous caustic otash concentratin caustic otash l e to.

a degree suiiicient that oncooling, while being stirred, a copious formation of anhydrous crystals of caustic potash takes place, then mixing with the thick pulp thus formed,

and while stirring, a caustic potash lye of name to this specification in the presence of lower percentage, and separating'the SOl1(l two subscrlblng Witnesses.

from the liquid at a temperature above that T at which the second lye melts and at'which H RICH REIT? temperature no separation of caustic potash \Vitnesses:

containing water takes place. FRANZ HAssLAoHER,

In testimony whereof I have signed my ERWIN DIPPEL. 

